A compressor such as a rotary compressor is widely used for a refrigerator-freezer, an air conditioner and the like because it is small in size and its structure is simple. A structure of the compressor such as the rotary compressor is described in a non-patent document 1. The structure of the conventional compressor will be explained using FIG. 11 based on the rotary compressor. FIG. 11 is a vertical sectional view of the conventional rotary compressor.
The rotary compressor shown in FIG. 11 includes a container 1, a compressor mechanism disposed on a lower portion of the container 1, and a motor disposed on an upper portion of the compressor mechanism. The compressor mechanism includes a shaft 2 having an eccentric portion 2a, a cylinder 3, a roller 4, a vane 5, a spring 6, an upper bearing member 7 having a discharge hole 7a, and a lower bearing member 8.
The motor has a stator 11 which includes a coil end 11c and a coil end 11d. The stator 11 is fixed to the inside of the container 1. The motor also includes a rotor 12 fixed to a shaft 2. The stator 11 is provided at its outer periphery with a plurality of notches 11e serving as passages of working fluid. A gap 13 is provided between the stator 11 and the rotor 12. A lower end surface 12a and an upper end surface 12b of the rotor 12 are respectively provided with a lower balance weight 13 and an upper balance weight 14 for eliminating unbalance around the center axis L of the shaft 2. The rotor 12 is provided at its lower end surface 12a and upper end surface 12b with a lower balance weight 14 and an upper balance weigh 15 for eliminating unbalance.
The container 1 includes an introducing terminal 18, a suction pipe 19, a discharge pipe 20, and an oil reservoir 21 provided in a lower portion of the container 1 for reserving refrigeration oil.
The operation of the rotary compressor having the above-described structure will be explained.
If the stator 11 is energized through the introducing terminal 18 to rotate the rotor 12, the roller 4 is eccentrically rotated by the eccentric portion 2a, and a volume of a space between the cylinder 3 and the roller 4 sandwiched between an upper bearing member 7 and a lower bearing member 8 is varied. With this, the working fluid is sucked from the suction pipe 19 and is compressed. The compressed working fluid is supplied from the oil reservoir 21 and is mixed with a refrigeration oil which lubricated the compressor mechanism and in this state, the working fluid is injected into a lower space 22 of the motor through the discharge hole 7a. 
The main flow of the injected working fluid collides against a lower end surface 12a of the rotor 12 and the lower balance weight 14 and then, generates a strong turning flow by the rotation of the rotor 12. A portion of oil drops mixed with the working fluid attaches to an inner wall of the container 1 by the centrifugal force or falls downward by the gravity and is separated from the working oil and returns into the oil reservoir 21 while the working fluid stays in the lower space 22 as the turning flow.
In a state in which the working fluid includes the oil drops which are not separated, the working fluid passes through the notches 11e and the gap 13, and is injected into an upper space 23 of the motor. The main flow of the injected working fluid flows toward the discharge pipe 20. At that time, a portion of the working fluid passes in the vicinity of an upper end surface 12b of the rotor 12 and the upper balance weight 15, and generates a turning flow due to the rotation of these elements. A portion of the oil drops included in the working fluid attaches to the inner wall of the container 1 by the centrifugal force while the working fluid stays in the upper space 23, or falls downward by the gravity and is separated from the working oil and returns into the oil reservoir 21 along the inner wall of the container 1 or a wall surface of the stator 11. The working fluid still including oil drops which are not yet separated from the working oil is discharged from the discharge pipe 20.
In the compressor, the working fluid and refrigeration oil which are compressed when a sliding surface of the compressor mechanism is lubricated are mixed, and a portion of the refrigeration oil reserved in the oil reservoir 21 is discharged out from the container 1 of the compressor during the process of the operation of the compressor. However, in the case of a compressor in which a large amount of refrigeration oil is discharged, since the oil level of the refrigeration oil in the oil reservoir 21 is lowered, the supply oil amount becomes insufficient, and the lubrication of the compression mechanism becomes insufficient, the reliability is deteriorated, the sealing of the compression mechanism becomes insufficient, and the efficiency of the compressor is deteriorated. Further, the refrigeration oil discharged from the compressor attaches to an inner wall of a tube of a heat exchanger to deteriorate the heat transfer coefficient between the working fluid and a wall surface in the heat exchanger tube. Thus, the performance of the refrigeration cycle is deteriorated. Therefore, the oil separating efficiency of the working fluid in the container 1 of the compressor is enhanced, and the discharging amount of the refrigeration oil is reduced.
As a structure for separating the refrigeration oil from the working fluid, there is a method to use an oil separating plate provided on an upper portion of the rotor 12 of the rotary compressor as shown in a patent document 1. FIG. 12 shows a detailed sectional view of a periphery of the oil separating plate of the conventional compressor.
The rotor 12 has an upper end plate 31a and a lower end plate 31b for closing the inserting holes of a permanent magnet 30. A plurality of through holes 12c are formed such as to penetrate the rotor 12 in the vertical direction. An oil separating plate 33 forms an oil separating space 32 in an upper portion of the rotor 12. The oil separating plate 33 is disposed above exits of the through holes 12c. The oil separating plate 33 is fixed by a fixing member 34.
In the compressor having the above-described structure, a portion of the working fluid including oil drops discharged into the lower space 21 of the motor from the compressor mechanism flows into the oil separating space 32 through the through holes 12c formed in the rotor 12. Here, the working fluid is discharged radially from an outer peripheral exit 32a of the oil separating plate 33 by the centrifugal force, and blows against the coil end 11d of the stator 11, and the working fluid and the refrigeration oil included in the working fluid are separated. Only the working fluid from which the refrigeration oil is separated flows upward, and is discharged out from the discharge pipe 19 provided on the upper portion of the container 1.
On the other hand, refrigeration oil attached to the coil end 11d of the stator 11 falls downward and returns into the oil reservoir 21 formed in the bottom of the container 1.
As a structure to prevent refrigeration oil from being mixed into the working fluid, there is a method in which an oil level stabilizing member is fixed to a bearing of the compressor as shown in patent document 2. FIG. 13 is a detailed sectional view of a periphery of the oil level stabilizing member of a conventional compressor.
That is, a disk-like oil level stabilizing member body (oil level stabilizing member) 228 is fixed to a lower surface of a bearing 225. An outer periphery of the oil level stabilizing member body 228 is formed with three holes having relatively large opening areas. Oil returns into an oil reservoir 220 through the holes. A foreign matter complementary net (oil level stabilizing member) 234 is placed on an upper surface of the outer periphery of the oil level stabilizing member body 228.
According to the compressor having such a structure, if a rotation shaft 205 is rotated, since a portion of the rotation shaft 205 is located in an oil reservoir, a centrifugal force is applied to oil in an oil reservoir tank 220. If the centrifugal force is applied to oil in the oil reservoir tank 220, a height of the oil in the vicinity of the rotation shaft 205 becomes low, and as a distance from the rotation shaft 205 becomes longer, the height of the oil becomes higher. Since the oil level stabilizing member body 228 is disposed, even if the oil level rises due to centrifugal force, the oil level is suppressed by the oil level stabilizing member body 228 and the foreign matter complementary net 234 placed on an upper surface of the body 228. Therefore, it is possible to prevent the oil level from being higher than the oil level stabilizing member body 228, and the oil level can be stabilized.
(Non-Patent Document 1)
“Air-Conditioning and Refrigeration handbook”, new edition 5, volume 11, machine”, Air-Conditioning and Refrigeration Institute, 1993, paragraphs 30 to 43
(Patent Document 1)
Japanese Patent Application Laid-open No. H8-28476 (paragraph 6, FIGS. 1 to 3)
(Patent Document 2)
Japanese Patent Application Laid-open No. 2003-328946 (page 6, FIGS. 1 to 4)
As described above, in the conventional compressor, the main flow of the working fluid injected into the lower space 22 of the motor from the discharge hole 7a of the compression mechanism collides against the lower end surface 12a of the rotor 12, the lower balance weight 14 and the like and then, produces a strong turning flow by the rotation of the rotor 12. At that time, an interface 24 between the working fluid and the refrigeration oil stored in the oil reservoir 21 is rippled, oil drops are torn from the interface 24 due to flow of the working fluid and is mixed into the working fluid. The oil drops supplied from the interface 24 to the working fluid increases the amount of oil drops included in the working fluid, and it becomes difficult to separate the oil drops from the working fluid.
To separate the oil drops from the working fluid, an oil separating plate shown in FIG. 12 is used. In this case, of the entire working fluid flowing from a lower space 22 to an upper space 23, this oil separating plate functions only for working fluid flowing through a through hole 12c, and it is impossible to separate the oil drops from the working fluid which passes through a notch 11e oil reservoir a gap 13. For this reason, there is a problem that a portion of the working fluid including oil drops supplied from the interface 24 passes through the notch 11e oil reservoir gap 13, and the oil separating plate 33 provided on an upper portion of the rotor 12 can not separate the oil drops.
To prevent refrigeration oil from being mixed into working fluid, there is a method in which an interface 24 which becomes higher as a distance from a rotation shaft 205 becomes longer due to centrifugal force caused by rotation of a rotation shaft 205 is suppressed using an oil level stabilizing member body 228 shown in FIG. 13, thereby stabilizing the interface 24. In this case, a discharging amount of refrigeration oil flowing from the compressor toward the refrigeration cycle, and a returning amount of refrigeration oil from the refrigeration cycle toward the compressor are varied and thus, the interface 24 of the compressor is always varied. Therefore, when the interface 24 is located lower than the oil level stabilizing member body 228, since the turning flow of the working fluid wields an influence on a portion below the oil level stabilizing member body 228, and there is a problem that the interface 24 is rippled by the turning flow of the working fluid, and the oil drops is torn from the interface 24 by the flow of the working fluid and is mixed into the working fluid. When the interface 24 is located higher than the oil level stabilizing member body 228, since the oil level stabilizing member body 228 is located below the interface 24 and can not exhibit its effect, there is a problem that the interface 24 is rippled by the turning flow of the working fluid, the oil drops are torn by the flow of the working fluid and the oil drops are mixed into the working fluid.
There is another method in which capacities of the lower space 22 and the upper space 23 are increased so that time during which the working fluid stays in such spaces is elongated, and separation of oil drops of refrigeration oil is facilitated by gravity. In this case, however, there is a problem the compressor is increased in size.
The above description is based on the vertical type rotary compressor, but the same is applied to the conventional scroll compressor of course. Irrespective of a difference between the vertical type and the lateral type or irrespective of a difference of the compressing manners, if the main flow working fluid passes in the vicinity of an end surface of the rotor and form a turning flow and the turning flow affects the interface while working fluid discharged from the compression mechanism is discharged from the discharge pipe provided on the container, the same problem is caused.
The above problems are generated irrespective of kinds of the working fluid, but especially when the refrigeration cycle uses a working fluid mainly comprising carbon dioxide as a main ingredient, since the pressure of the working fluid discharged from the compression chamber exceeds a critical pressure, the working fluid in the container is brought into a supercritical state, an amount of refrigeration oil solved in the working fluid is increased, and a density ratio between the working fluid and the refrigeration oil is reduced by about half as compared with conventional flon or the like. Therefore, there is a problem that it becomes more difficult to separate the oil using gravity or centrifugal force.
Therefore, the present invention has been accomplished to solve the above problems, and it is an object of the invention to provide a compressor in which oil drops is prevented from being torn from an interface between working fluid and refrigeration oil stored in an oil reservoir, an amount of refrigeration oil taken out from outside from a container is reduced, the reliability of a compressor is enhanced, and efficient refrigeration cycle can be obtained.